Helium enclosed compressor

ABSTRACT

The helium enclosed compressor uses a helium gas as a working gas, houses a compressor section and a motor section including a stator having coil ends and a stator within an enclosed vessel, and discharges the helium gas, which has been discharged into the enclosed vessel from a discharge port of the compressor section, to the outside of the enclosed vessel through the coil ends. A plurality of varnish-treated layers which becomes insulating films is formed on the surface of a coil which constitutes the coil ends. Thereby, a helium enclosed compressor capable of preventing insulation breakdown of the coil ends caused by corona discharge is obtained.

BACKGROUND OF THE INVENTION

The present invention relates to a helium enclosed compressor, andparticularly, to one suitable for a helium enclosed compressor in whicha motor section having coil ends is housed within an enclosed vesselfilled with a helium gas.

In a conventional helium enclosed compressor, a helium gas is used as aworking gas, a compressor section and a motor section are arrangedvertically and housed within an enclosed vessel, the inside of theenclosed vessel is partitioned into a discharge chamber and a motorchamber by a frame, a first rectangular passage which allows thedischarge chamber to communicate with the motor chamber is providedbetween an outer peripheral surface of the frame and an inner wallsurface of the enclosed vessel, and a second passage which allows anupper motor chamber to communicate with a lower motor chamber isprovided between an outer peripheral surface of the stator and the innerwall surface of the enclosed vessel. Also, the compressor section isadapted such that a stationary scroll and an orbiting scroll are made tomesh with each other while their wraps face the inside, and the orbitingscroll is made to orbit, thereby sucking the helium gas from a suctionport of an outer peripheral portion of the stationary scroll, anddischarging the helium gas into the motor chamber through the inside ofthe discharge chamber from a discharge port of a central portion of thestationary scroll. Additionally, the helium enclosed compressor includesan oil injection mechanism section which connects an oil injection pipefor cooling the helium gas to an oil injection port provided in thepanel of the stationary scroll through the enclosed vessel, and aninverter which controls the number of rotations of the motor section.

As a document relevant to the helium enclosed compressor, for example,JP-A-2006-29251 is mentioned.

In the helium scroll compressor, the peripheries of the coil ends arefull of a helium gas. Therefore, it turned out that there are problemsinherent in helium applications that corona discharge occurs easily in ahelium gas atmosphere, and thereby, the insulating property of the motorcoil ends deteriorates. Particularly when the number of rotations of themotor section is controlled by an inverter, a high voltage surge voltageis generated on the side of the inverter, and the high surge voltageacts on the coil ends. Therefore, the corona discharge occurs easily.

However, in the conventional helium scroll compressor, a varnish-treatedlayer formed on the surface of a coil which constitutes the coil endswas a monolayer, and it could not be said that prevention of a coronadischarge was fully considered.

DISCLOSURE OF THE INVENTION

The object of the invention is to obtain a helium enclosed compressorcapable of preventing insulation breakdown of coil ends by coronadischarge to improve reliability.

In order to achieve the aforementioned object, a first aspect of theinvention is a helium enclosed compressor in which a helium gas is usedas a working gas, a compressor section and a motor section including astator having coil ends, and a rotor is housed within an enclosedvessel, and the helium gas, which has been discharged into the enclosedvessel from a discharge port of the compressor section, is discharged tothe outside of the enclosed vessel through the coil ends. Here, aplurality of varnish-treated layers which becomes insulating films isformed on the surface of a coil which constitutes the coil ends.

Additionally, a second aspect of the invention is a helium enclosedcompressor in which a helium gas is used as a working gas, a compressorsection, and a motor section including a stator having coil ends and arotor are arranged vertically and housed within an enclosed vessel, theinside of the enclosed vessel is partitioned into a discharge chamberand a motor chamber by a frame, a first rectangular passage which allowsthe discharge chamber to communicate with the motor chamber is providedbetween an outer peripheral surface of the frame and an inner wall ofthe enclosed vessel, a second passage which allows an upper motorchamber in an upper portion of the stator to communicate with a lowermotor chamber having an oil reservoir at a bottom of a lower portion ofthe stator is provided between an outer peripheral surface of the statorand the inner wall of the enclosed vessel, the compressor section isadapted such that a stationary scroll having a spiral wrap standingupright at a disk-like panel and an orbiting scroll having a spiral wrapstanding upright at a disk-like panel are made to mesh with each otherwhile their wraps face the inside, and the orbiting scroll is made toorbit, thereby sucking the helium gas from the suction port of an outerperipheral portion, and discharging the helium gas into the dischargechamber from a discharge port of a central portion of the stationaryscroll, and an oil injection mechanism section is provided to connect anoil injection pipe for cooling the helium gas to an oil injection portprovided in the panel of the stationary scroll through the enclosedvessel. Here, a plurality of varnish-treated layers which becomesinsulated films is formed on the surface of a coil which constitutes thecoil ends, and the external diameter of the coil end on the downstreamside of the first passage is increased to increase the coil density ofthe coil ends, and the gap dimension between outer peripheries of thecoil ends and the inner wall of the enclosed vessel is made smaller thanthe height of an opening of the first passage.

In the first and second aspects of the invention as described above, ifthe invention is applied to one including an inverter which controls thenumber of rotations of the motor section, a large effect is obtained.More preferably, an enamel-coated coil is used as the coil whichconstitutes the coil ends, and an epoxy-based varnish material is usedfor the varnish-treated layers.

A third aspect of the invention is a helium enclosed compressor in whicha helium gas is used as a working gas, a compressor section, and a motorsection including a stator having coil ends and a rotor are housedwithin an enclosed vessel, the inside of the enclosed vessel ispartitioned into a discharge chamber and a motor chamber by a frame, thecompressor section is adapted such that a stationary scroll having aspiral wrap standing upright at a disk-like panel and an orbiting scrollhaving a spiral wrap standing upright at a disk-like panel are made tomesh with each other while their wraps face the inside, and the orbitingscroll is made to orbit, thereby sucking the helium gas from a suctionport of an outer peripheral portion of the stationary scroll, anddischarging the helium gas into the discharge chamber from a dischargeport of a central portion of the stationary scroll, and an inverter isprovided to control the number of rotations of the motor section. Here,a plurality of varnish-treated layers which becomes insulating films isformed on the surface of a coil which constitutes the coil ends.

In a more preferable concrete configuration of the third aspect of theinvention as described above, the operating pressure within the enclosedvessel is set to a range of 1.5 MPaG to 3.0 MPaG.

More preferable concrete configurations in the second and third aspectsof the invention described above are as follows.

That is, the stator has a stator core and the coil ends which protrudeon both sides of the stator core, a core cut portion is formed in theouter peripheral surface of the stator core so that a passage whichallows an upper portion and a lower portion of the stator core tocommunicate with each other is provided between an outer peripheralsurface of the stator core and the inner wall surface of the enclosedvessel, and the external diameter of the coil ends is increased to anexternal diameter almost equal to the external diameter of the statorcore in the core cut portion, thereby increasing the coil density of thecoil ends.

According to the helium enclosed compressor of the invention describedabove, it is possible to prevent insulation breakdown of coil ends bycorona discharge to improve reliability.

Other features, objects, and advantages of the invention will becomemore apparent on reading the following description with reference to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view of a helium enclosed scrollcompressor of a first embodiment of the invention,

FIG. 2 is an A-A sectional view of FIG. 1,

FIG. 3 is a B-B sectional view of FIG. 1,

FIG. 4 is a sectional view in a state where a stator used for a motorsection of FIG. 1 is arranged transversely,

FIG. 5 is a plan view of the stator used for the motor section of FIG.1,

FIG. 6 is an enlarged cross-sectional view of a coil portion in coilends of this embodiment of FIG. 4,

FIG. 7 is an enlarged cross-sectional view of a coil portion in coilends of a conventional example of FIG. 4,

FIG. 8 is a longitudinal sectional view of a helium enclosed scrollcompressor of a second embodiment of the invention,

FIG. 9 is a graph illustrating respective corona starting voltagecharacteristics of a plurality of varnish-treated layers of the secondembodiment and a single varnish-treated layer of the conventionalexample, and

FIG. 10 is a graph illustrating respective operation ranges of thesecond embodiment and the conventional example.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, a plurality of embodiments of the invention will bedescribed with reference to the drawings. The same reference numerals inthe drawings of each embodiment represent the same objects orequivalents.

First Embodiment

A helium scroll compressor of a first embodiment of the invention willbe described with reference to FIGS. 1 to 7.

First, referring to FIG. 1, the basic configuration of a helium enclosedscroll compressor 100 of this embodiment will be described. FIG. 1 is alongitudinal sectional view of the helium enclosed scroll compressor 100of the first embodiment of the invention.

The helium enclosed scroll compressor 100 uses a helium gas as a workinggas, and includes a compressor section 2 and a motor section 3 which arelocated vertically within an enclosed vessel 1 and housed juncturally bya rotary shaft 14, and an oil injection mechanism section 60 whichinjects lubricating oil 23 stored at the bottom of the enclosed vessel 1into a compression chamber 8 of the compressor section 2.

The compressor section 2 has a stationary scroll 5 having a spiral wrap5 b standing upright at a panel 5 a, and an orbiting scroll 6 having aspiral wrap 6 b standing upright at an panel 6 a. The wraps 5 b and 6 bare made to mesh with each other while they face the inside, theorbiting scroll 6 is engaged with an eccentric shaft 14 a connected to arotary shaft 14, and the orbiting scroll 6 is made to orbit with respectto the stationary scroll 5 without rotating. The stationary scroll 5 isprovided with a discharge port 10 which opens to a central portion, anda suction port 15 which opens to an outer peripheral portion. By theorbiting motion of the orbiting scroll 6, the compressor section 2 sucksa working gas from the suction port 15 by the orbiting scroll 6, movesthe working gas about the compression chamber 8 formed by the stationaryscroll 5 and the orbiting scroll 6 to reduce volume to compress theworking gas, and discharges the compressed working gas into a dischargechamber la in an upper portion of the compressor section 2 from thedischarge port 10.

The motor section 3 includes a stator 3 a which forms a plurality ofarched passages (second passages) 25 a to 25 d (refer to FIG. 3) betweenthe motor section and the enclosed vessel 1, and a rotor 3 b which isrotatably provided inside the stator 3 a. The stator 3 a has a statorcore 3 f, and coil ends 3 c and 3 d which protrude up and down from thestator core 3 f. The plurality of arched passages 25 a to 25 d isprovided by forming a plurality of core cut portions 3 q to 3 t at anouter peripheral surface of the stator core 3 f.

Also, the helium enclosed scroll compressor 100 is adapted to guide theworking gas discharged along with injection oil to an upper motorchamber 1 b 1 of a motor chamber 1 b in a lower portion of thecompressor section 2 through a rectangular passage (first passage) 18formed between the compressor section 2 and the enclosed vessel 1, toguide the working gas to a lower motor chamber 1 b 2 in a lower portionof the motor section 3 through an arched passage 25 b formed between thestator core 3 a and the enclosed vessel 1, to guide the working gas tothe upper motor chamber 1 b 1 in an upper portion of the motor section 3through another arched passage 25 c formed between the stator core 3 aand the enclosed vessel 1, and to discharge the working gas to theoutside through a discharge pipe 20. The discharge pipe 20 is locatedand provided opposite the rectangular passage 18. The arched passage 25b is provided to face a vertical direction directly under therectangular passage 18.

Next, the entire configuration of the helium enclosed scroll compressor100 will be described more concretely, referring to FIGS. 1 to 3. FIG. 2is an A-A sectional view of FIG. 1, and FIG. 3 is a B-B sectional viewof FIG. 1.

In this embodiment, as described above, a helium gas is used as aworking gas, and the oil injection pipe 31 for cooling this workinghelium gas is connected to an oil injection port 22 provided at thepanel 5 a of the stationary scroll 5 through a top cover 1 c of theenclosed vessel 1. Oil is injected into the compression chamber 8 duringthe compression of the compressor section 2 through the oil injectionport 22 from the oil injection pipe 31. Additionally, the bottom of theenclosed vessel 1 is provided with an oil take-out pipe 30 which takesout lubricating oil 23 at the bottom of the vessel to the outside of thevessel.

In the compressor section 2, the stationary scroll 5 and the orbitingscroll 6 are engaged with each other to form the compression chamber 8.The stationary scroll 5 is comprised of the disk-like panel 5 a, and thewrap 5 b which stands upright at the panel and is formed in the shape ofan involute curve or a curve approximate thereto, the central portionthereof is provided with the discharge port 10, and the outer peripheralportion thereof is provided with the suction port 15. The orbitingscroll 6 is comprised of the disk-like panel 6 a, the wrap 6 b whichstands upright at the panel and formed in the same shape as the wrap 5 bof the stationary scroll, and a boss 6 c which is formed on the surfaceof the panel opposite the wrap.

A frame 7 partitions the inside of the enclosed vessel 1 into thedischarge chamber la on the side of the compressor section 2 and themotor chamber lb on the side of the motor section 3. The rectangularpassage 18 is constituted by passages 18 a and 18 b which are formedbetween outer edges of the stationary scroll 5 and the frame 7 and aninner wall surface 1 m of the enclosed vessel 1. A central portion ofthe frame 7 is provided with a bearing 40, and the rotary shaft 14 isborne by the bearing 40. Additionally, the frame 7 fixes the stationaryscroll 5 by a plurality of bolts 81.

The eccentric shaft 14 a which constitutes an upper end of the rotaryshaft 14 is inserted into the boss 6 c so as to allow an orbitingmotion. The orbiting scroll 6 is borne on the frame 7 by an Oldham'smechanism 38 comprised of an Oldham's ring and an Oldham's key, and theorbiting scroll 6 is formed so as to orbit with respect to thestationary scroll 5 without rotating. The rotary shaft 14 is integrallyconnected to the motor shaft 14 b, and is directly connected to themotor section 3.

A suction pipe 17 is connected to the suction port 15 of the stationaryscroll 5 through the top cover 1 c of the enclosed vessel 2. Thedischarge chamber la to which the discharge port 10 opens communicateswith the motor chamber 1 b via the passage 18 (18 a, 18 b) of the outeredge (outer edges of the stationary scroll 5 and the frame 7) of thecompressor section 2. The motor chamber 1 b communicates with thedischarge pipe 20 passing through a casing portion 1 d which constitutesthe central portion of the enclosed vessel 1. The discharge pipe 20 isinstalled in a position substantially opposite the passages 18 a and 18b. The positional relationship between both passages 18 and thedischarge pipe 20 is such that a mixture of the working gas andinjection oil which has passed through the passage 18 is divided intotwo including a downward flow path facing the arched passage 25 b in thevertical direction of the passage 18, and a flow path which faces ahorizontal direction by the collision with a stator upper surface or thecoil end 3 c therearound. The horizontal flow path is branched into aflow path which faces the arched passages 25 a and 25 d along a vesselinner wall and a flow path which faces the discharge pipe 20 through thecentral portion.

Between the stator 3 a and the inner wall surface 1 m of the casingportion 1 d, the motor section 3 forms the arched passage 25 b whichbecomes a flow passage portion of the mixture of a working gas andinjection oil, and forms the arched passages 25 a, 25 c, and 25 dserving as other flow passage portions. The mixture of a working gas andinjection oil becomes mainly a downward flow in the arched passage 25 b,and only the working gas becomes an upward flow in the arched passage 25c. Additionally, an air gap 26 between the stator 3 a and the rotor 3 balso becomes a gas passage, and the motor chamber 1 b 1 and the motorchamber 1 b 2 communicate with each other via the air gap 26.

By the flow of a mixture of a working gas and injection oil of the motorchambers 1 b 1 and 1 b 2 inside such a vessel, direct cooling of themotor section 3 by the working gas including injection oil having arelatively low temperature of 60° C. to 70° C. is allowed. Additionally,the oil in the working gas is separated from the working gas in themotor chambers 1 b 1 and 1 b 2, flows downward, and is stored at thebottom of the enclosed vessel 1.

A hermetic terminal 70 is attached to the enclosed vessel 1, andsupplies electric power to the motor section 3 via a motor lead wire 3m.

In addition, an O ring 53 which seals a high-pressure portion and alow-pressure portion is provided between the suction pipe 17 and thestationary scroll 5. Additionally, check valve means 13 is providedwithin the suction pipe 17. The check valve 13 is provided to preventreverse rotation of the rotary shaft 14 when the compressor is stoppedand to prevent the lubricating oil 23 within the enclosed vessel 1 fromflowing out to the low-pressure side.

Additionally, a back surface of the panel 6 a of the orbiting scroll 6is provided with a space 36 (hereinafter referred to as a backpressurechamber) surrounded by the compressor section 2 and the frame 7. Anintermediate pressure Pb between a suction pressure Ps and a dischargepressure Pd is introduced into the backpressure chamber 36 via pores 6 dwhich are perforated in the panel 6 a of the orbiting scroll 6, therebyapplying an axial application force which presses the orbiting scroll 6against the stationary scroll 5.

The lubricating oil 23 is reserved at the bottom of the enclosed vessel1. The lubricating oil 23 is sucked up by the differential pressurebetween the high pressure within the enclosed vessel 1 and theintermediate pressure Pb of the backpressure chamber 36 to an oilsuction upper pipe 27, flows through the inside of the rotary shaft 14,and is fed to a main bearing 40 and an auxiliary bearing 39 via theturning bearing 32 and a transverse hole 51. The oil fed to the mainbearing 40 and the auxiliary bearing 39 passes through the backpressurechamber 36, is injected into the compression chamber 8 of the scrollwrap via the pores 6 d, mixed with compressed gas, and discharged to thedischarge chamber la along with the helium gas.

Next, a lubrication system by the oil injection of the helium enclosedscroll compressor 100 will be described more concretely, referring toFIG. 1.

The lubricating oil 23 reserved at the bottom of the enclosed vessel 1flows into the oil take-out pipe 30 from an inflow portion 30 a of theoil take-out pipe 30 by the differential pressure between the pressure(discharge pressure Pd) within the enclosed vessel 1 and the pressure(pressure lower than the discharge pressure Pd) of the compressionchamber 8. The oil which has flowed into the inflow portion 30 a of theoil take-out pipe 30 reaches an oil cooler 33 through an external oilpipe 51, and is appropriately cooled here. Then, the oil passes throughthe oil injection pipe 31 and the port 22 via oil pipes 52 a and 52 b,and is injected into the compression chamber 8 by utilizing thedifferential pressure. In addition, in FIG. 1, reference numeral 271represents an oil flow rate control valve.

The oil injected into the compression chamber 8 in this manner functionsto cool the working gas and lubricate sliding portions, such as the tipof the scroll wrap, within the compression chamber 8. Also, the oilsupplied to the compression chamber 8 from the lubrication system by oilinjection and the oil fed to the compression chamber 8 through the mainbearing 40 and the auxiliary bearing 39 are discharged to the dischargechamber 1 a from the discharge port 10 along with the working gas, andbecomes the flow of a mixed fluid of the helium gas and a mist-like oil.This mixed fluid moves to the motor chamber 1 b via the rectangularpassages 18 a and 18 b. As a result, as mentioned above, the mixed fluidis separated from the working gas in the motor chamber 1 b, flows downvia the arched passage 25 and the like, and is reserved at the bottom ofthe enclosed vessel 2.

Next, the coil ends 3 c and 3 d of the motor section 3 will be describedmore concretely, referring to FIG. 1 and FIGS. 4 to 7. FIG. 4 is asectional view in a state wherein the stator 3 a used for the motorsection 3 of FIG. 1 is arranged transversely, FIG. 5 is a plan view ofthe stator 3 a used for the motor section 3 of FIG. 1, FIG. 6 is aenlarged cross-sectional view of a coil portion in the coil ends 3 c and3 d of this embodiment of FIG. 4, and FIG. 7 is an enlargedcross-sectional views of a coil portion in coil ends 3 c′ and 3 d′ of aconventional example of FIG. 4.

The coil ends 3 c and 3 d indicated by solid lines of FIGS. 4 and 5 areformed to have greater external diameter Dc and height Lm1 and Lm2 andare formed to have greater coil density, than the coil ends 3 c′ and 3d′ indicated by one-dotted chain lines of the conventional example. Thismakes it possible to reduce the amount of coil shaping in electric workduring coil shaping compared with the conventional example, and makes itpossible to suppress generation of any damage of coils during electricwork. Accordingly, generation of corona discharge resulting from thegeneration of the coil damage can be suppressed.

In addition, in this embodiment, a height Lm1 of the coil end 3 c ismade equal to a height Lm2 of the coil end 3 d. Additionally, it ispractically appropriate that the relationship between a stator externaldiameter Ds and heights Lm1 and Lm2 is Lm1/Ds=Lm2/Ds=0.26 to 0.30.

Additionally, the coil ends 3 c and 3 d are expanded to an externaldiameter Dc almost equal to an external diameter Lc of the stator core 3f in the core cut portions 3 q to 3 t. This makes it possible to reducethe amount of coil shaping while securing the passage area of the archedpassages 25 a to 25 d.

Furthermore, as shown in FIG. 1, the external diameters of the coil ends3 c and 3 d are enlarged such that a gap dimension S1 between the outerperiphery of the coil ends 3 c or 3 d and the inner wall surface 1 m ofthe enclosed vessel 1 becomes smaller than a height H1 of the opening ofthe rectangular passage 18 b. Thereby, a mixture of oil and a helium gaswhich flows down from the opening of the rectangular passage 18 bdirectly collides with the upper surface of the coil end 3 c. As aresult, oil separation performance within the enclosed vessel 1 can beimproved, and so-called amount of rise of oil which flows out to theoutside from the enclosed vessel 1 can be reduced markedly. Inparticular, since collision separation performance is exhibited easilyunder an overload pressure condition in which gas flow rate becomes thegreatest, the amount of rise of oil can be further reduced. The heliumenclosed compressor is used for a cryopump device mainly used for asemiconductor manufacturing apparatus. In this case, by virtue of thereduction of the amount of rise of oil, the lifespan of an oil adsorberto be loaded on a helium compressor unit extends, an effect is alsoexerted on the long lifespan of the maintenance time of the heliumcompressor unit and the reduction of maintenance cost, and an effectinherent in the helium enclosed compressor is obtained.

Moreover, as shown in FIG. 6, a plurality of varnish-treated layers 50which becomes insulating films is formed on the surface of a coil 3 ewhich constitutes the coil ends 3 c and 3 d of this embodiment. As thevarnish coating material of the varnish-treated layers 50, a highepoxy-based varnish material having an electrical insulating property isused. The plurality of varnish-treated layers 50 is comprised of a firstvarnish-treated layer 50 a and a second varnish-treated layer 50 b whichare formed by carrying out varnish treatment multiple times (two timesin the illustrated example). This varnish treatment is performed byimmersing and taking out the coil ends 3 c and 3 d in/from a varnishtank and by repeating this multiple times. In contrast, as shown in FIG.7, a single varnish-treated layer 50′ which becomes an insulating filmis formed on the surface of the coil 3 e which constitutes the coil ends3 c′ and 3 d′ of the conventional example.

In this embodiment, in order to form the plurality of varnish-treatedlayers 50, the Dc/Ds value which becomes the ratio of an externaldiameter Dc of the upper or lower coil end 3 c or 3 d of the motorsection 3 and the external diameter Ds of the stator 3 a is set to about0.95, and the density of the coil 3 e is made larger than that of theconventional example. The density of the coil 3 e is roughly expressedby coil cross-sectional area/whole occupying area. As this value becomeslarger, the gap between the coils 3 e becomes small, and the possibilitythat the coil 3 e contact each other increases. When the coils 3 econtact each other, this becomes a factor that any damage to the coil 3e is caused. The density of the coil 3 e of the conventional example isabout 50%, whereas the density of the coil 3 e of this embodiment isabout 40%, and is reduced by about twenty percent in terms of ratio.Even from this point, in this embodiment, generation of any coil damageduring electric work can be suppressed, and generation of coronadischarge resulting from the generation of the coil damage can besuppressed.

As the coils 3 e of the coil ends 3 c and 3 d of this embodiment of thecoil ends 3 c′ and 3 d′ of the conventional example, enamel-coated(polyester-based film insulating material) electric wires are used. Thefirst varnish-treated layer 50 a and varnish-treated layer 50′ with athickness A1 are formed on the surfaces of the coils 3 e by immersingthe enamel-coated coils 3 e in a varnish tank to perform first varnishtreatment. This thickness A1 is, for example, about several micrometers.Only in forming the first varnish-treated layer 50 a and varnish-treatedlayer 50′ by the first varnish treatment, a non-varnish-treated portionor a very thin varnish-treated portion which has not covered the coil 3e may be generated partially, which causes generation of coronadischarge. Particularly, in a case where a minute pinhole (bus exposedportion) exists in the enamel coating of the surface of the coil 3 e,corona discharge occurs easily when the pinhole and thenon-varnish-treated portion or the very thin varnish-treated portionoverlap each other.

Thus, in this embodiment, the plurality of varnish-treated layers 50with a thickness A2 is formed on the surface of the coil 3 e byimmersing the coil ends 3 c and 3 d in which the first varnish-treatedlayer 50 a has been formed to perform second varnish treatment. Theplurality of varnish-treated layers 50 is comprised of the firstvarnish-treated layer 50 a and the second varnish-treated layer 50 b.The thickness A2 becomes an insulating film thickness of about twice thethickness A1 of the varnish-treated layer 50′ of the conventionalexample. Since the second varnish-treated layer 50 b is formed so as tocover the non-varnish-treated portion or very thin varnish-treatedportion in the first varnish-treated layers 50 a, generation of coronadischarge can be prevented. Additionally, gaps L3 to L5 between thecoils 3 e become wider than gaps L1 to L2 of the conventional example byincreasing the density of the coil 3 e, and a varnish material permeateseasily during varnish treatment. As a result, even when there is aminute pinhole formed in the surface of the coil 3 e, the minute pinholeportion can be covered reliably, and the insulating property as thewhole motor can be improved remarkably.

When the plurality of varnish-treated layers 50 is formed on the surfaceof the coil 3 e of the coil end 3 c or 3 d, the heat-radiatingcharacteristic from this portion deteriorates. Thus, in this embodiment,as described above, measures are taken, such as achieving motor coolingby oil injection, promoting the cooling effect of oil to the coil 3 e asthe mixture of the oil and a helium gas which flows down from therectangular passage 18 b directly collides with the upper surface of thecoil end 3 c, and increasing the density of the coil 3 e, therebyfacilitating permeation of oil to between the coils 3 e to promote thecooling effect of oil to the coil 3 e. Thereby, even under severetesting conditions, such as an overload condition, the temperature riseof the coil ends 3 c and 3 d can be prevented, and lowering of the motorlifespan and degradation of reliability by motor burnout can beprevented.

Second Embodiment

Next, a second embodiment will be described with reference to FIGS. 8 to10. FIG. 8 is a longitudinal sectional view of a helium enclosed scrollcompressor 100 of the second embodiment of the invention, FIG. 9 is agraph showing respective corona starting voltage characteristics of theplurality of varnish-treated layers of the second embodiment and asingle varnish-treated layer of the conventional example, and FIG. 10 isa graph showing respective operation ranges of the second embodiment andthe conventional example. Since this second embodiment is different fromthe first embodiment in points to be described below, and is basicallythe same as the first embodiment in other points, redundant descriptionis omitted.

This second embodiment is an example of an enclosed helium scrollcompressor to be driven by an inverter 400. In this second embodiment,the hermetic terminal 70 which is connected to the motor section 3 viathe motor lead wire 3 m is installed in the casing portion 2 b of theenclosed vessel 1. This hermetic terminal 70 is supplied with acommercial power supply voltage through a wiring line 450, the inverter400, and a wiring line 390 from a commercial power supply 500.

For example, in the commercial power supply 480 V of U.S. areas or thelike, the surge voltage to be generated by inverter driving is thegreatest, and the high voltage of 2×480×√{square root over ( )}2=about1400 V acts on the hermetic terminal 70, and between the coils 3 e ofthe coil end 3 c or 3 d. Even if a high surge voltage acts on betweenthe coils 3 e of the coil end 3 c or 3 d, similarly to the firstembodiment, the film thickness of a varnish insulating material is setto be multiple times the thickness in the conventional one-time varnishtreatment, and even if a pin hole or the like is interposed in anenameled wire of a coil portion, coating of a varnish insulatingmaterial is performed reliably. Thereby, the insulation breakdown effectby corona discharge can be prevented, and short-circuiting by any damageof the coil 3 e can be prevented.

In this embodiment, the operating pressure within the enclosed vessel isset to a range of 1.5 MPaG to 3.0 MPaG by the inverter 400. This makesit possible to reliably prevent generation of corona discharge.

This will be described concretely with reference to FIGS. 9 and 10. FIG.9 shows the relationship between the atmospheric pressure of a heliumgas and the corona discharge starting voltage. A C characteristic curveshows the conventional example in which varnish treatment was performedonce, a B characteristic curve shows the second embodiment in whichvarnish treatment was performed twice, and an A characteristic curveshows a case in which varnish treatment was performed three times. Assuch, it turned out that the corona discharge starting voltage has agreat influence on an atmospheric pressure along with the influence ofthe number of times of varnish treatment, and it also turned out that avery high corona discharge starting voltage can be obtained byperforming a plurality of layers of varnish treatment and by setting thepressure (that is, the pressure within the enclosed vessel 1) of ahelium gas around the motor section 3 to 1.5 MPaG. From this result, inthe helium scroll compressor which performs inverter control, as shownin FIG. 10, the motor insulating property breakdown by a surge voltagegenerated by inverter driving can be reliably prevented if the pressurewithin the vessel under operation is set to 1.5 MPaG or more. Inaddition, the upper limit 3.0 MPaG is a constraint on the strength ofthe enclosed vessel 1.

The lubricating oil 23 is reserved at the bottom of the enclosed vessel1, and the height Lm2 of the lower coil end 3 d is increased so that thelower end of the coil end 3 d is soaked in an oil surface 23 c. Thismakes it possible to more reliably cool the motor section 3.

According to the first and second embodiments described above, thehelium enclosed compressor for constant speed and for inverter drivinghas the following effects.

(1) By forming a plurality of varnish-treated layers which becomesinsulating films on the surface of a coil which constitutes coil ends,it is possible to set the film thickness of a varnish insulatingmaterial to be several times larger than a conventional one, and theinsulation deterioration and insulation breakdown of the coil endscaused by corona discharge can be prevented.

(2) Even if a defective portion, such as a pinhole portion or coildamage, is interposed in the surface of the motor coil end, the abovevarnish insulating material permeates easily, and the varnish-treatedlayer can cover the defective portion completely. For this reason, amotor insulating property can be improved remarkably, and motor burnoutcan be prevented in advance.

(3) By relaxing the geometry of the motor coil end, any damage to thewhole coil portion during shaping of the coil end can be reduced, andgeneration of coil damage can be suppressed. For this reason, a motorinsulating property is improved and the reliability of a motor can beimproved.

(4) Since the function of the motor coil end as a demister for oilseparation is improved, the oil separation efficiency of the vesselitself of the compressor is improved, and the amount of rise of oil ofthe compressor can be reduced.

1. A helium enclosed compressor in which a helium gas is used as aworking gas, a compressor section, and a motor section including astator having coil ends, and a rotor is housed within an enclosedvessel, and the helium gas, which has been discharged into the enclosedvessel from a discharge port of the compressor section, is discharged tothe outside of the enclosed vessel through the coil ends, wherein aplurality of varnish-treated layers which becomes insulating films isformed on the surface of a coil which constitute the coil ends.
 2. Thehelium enclosed compressor according to claim 1, further comprising aninverter which controls the number of rotations of the motor section. 3The helium enclosed compressor according to claim 1, wherein anenamel-coated coil is used as the coil which constitutes the coil ends,and an epoxy-based varnish material is used for the varnish-treatedlayers.
 4. A helium enclosed compressor in which a helium gas is used asa working gas, a compressor section, and a motor section including astator having coil ends and a rotor are arranged vertically and housedwithin an enclosed vessel, the inside of the enclosed vessel ispartitioned into a discharge chamber and a motor chamber by a frame, afirst rectangular passage which allows the discharge chamber tocommunicate with the motor chamber is provided between an outerperipheral surface of the frame and an inner wall surface of theenclosed vessel, a second passage which allows an upper motor chamber inan upper portion of the stator to communicate with a lower motor chamberhaving an oil reservoir at a bottom of a lower portion of the stator isprovided between an outer peripheral surface of the stator and the innerwall surface of the enclosed vessel, the compressor section is adaptedsuch that a stationary scroll having a spiral wrap standing upright at adisk-like panel and an orbiting scroll having a spiral wrap standingupright at a disk-like panel are made to mesh with each other whiletheir wraps face the inside, and the orbiting scroll is made to orbit,thereby sucking the helium gas from a suction port of an outerperipheral portion of the stationary scroll, and discharging the heliumgas into the discharge chamber from a discharge port of a centralportion of the stationary scroll, and an oil injection mechanism sectionis provided to connect an oil injection pipe for cooling the helium gasto an oil injection port provided in the panel of the stationary scrollthrough the enclosed vessel, wherein a plurality of varnish-treatedlayers which becomes insulating films is formed on the surface of a coilwhich constitutes the coil ends, and the external diameter of the coilend on the downstream side of the first passage is increased to increasethe coil density of the coil ends, and the gap dimension between outerperipheries of the coil ends and the inner wall surface of the enclosedvessel is made smaller than the height of an opening of the firstpassage.
 5. The helium enclosed compressor according to claim 4, whereinan enamel-coated coil is used as the coil which constitutes the coilends, and an epoxy-based varnish material is used for thevarnish-treated layers.
 6. The helium enclosed compressor according toclaim 4, wherein the stator has a stator core and the coil ends whichprotrude on both sides of the stator core, a core cut portion is formedin the outer peripheral surface of the stator core so that a passagewhich allows an upper portion and a lower portion of the stator core tocommunicate with each other is provided between an outer peripheralsurface of the stator core and the inner wall surface of the enclosedvessel, and the external diameter of the coil ends is increased to anexternal diameter almost equal to the external diameter of the statorcore in the core cut portion, thereby increasing the coil density of thecoil ends.
 7. A helium enclosed compressor in which a helium gas is usedas a working gas, a compressor section, and a motor section including astator having coil ends and a rotor are housed within an enclosedvessel, the inside of the enclosed vessel is partitioned into adischarge chamber and a motor chamber by a frame, the compressor sectionis adapted such that a stationary scroll having a spiral wrap standingupright at a disk-like panel and an orbiting scroll having a spiral wrapstanding upright at a disk-like panel are made to mesh with each otherwhile their wraps face the inside, and the orbiting scroll is made toorbit, thereby sucking the helium gas from a suction port of an outerperipheral portion of the stationary scroll, and discharging the heliumgas into the discharge chamber from a discharge port of a centralportion of the stationary scroll, and an inverter is provided to controlthe number of rotations of the motor section, wherein a plurality ofvarnish-treated layers which becomes insulating films is formed on thesurface of a coil which constitutes the coil ends.
 8. The heliumenclosed compressor according to claim 7, wherein the operating pressurewithin the enclosed vessel is set to a range of 1.5 MPaG to 3.0 MPaG. 9.The helium enclosed compressor according to claim 7, wherein the statorhas a stator core and the coil ends which protrude on both sides of thestator core, a core cut portion is formed in the outer peripheralsurface of the stator core so that a passage which allows an upperportion and a lower portion of the stator core to communicate with eachother is provided between an outer peripheral surface of the stator coreand the inner wall surface of the enclosed vessel, and the externaldiameter of the coil ends is increased to an external diameter almostequal to the external diameter of the stator core in the core cutportion, thereby increasing the coil density of the coil ends.